President Bush has solidified his standing in two new public opinion polls as he prepares to debate his Democratic challenger, Senator John Kerry, on Thursday in Florida. Televised presidential debates have often provided opportunities for both incumbents and challengers.

Two new polls, one by Gallup and another by the Washington Post, give the president a lead over Senator Kerry by six to eight points.

Democrats say that reinforces their view that the pressure is on Senator Kerry in Thursday's debate to more clearly define his differences on Iraq and other issues with President Bush.

"The debates are a chance for people who really don't know what he [Kerry] stands for to hear directly from him what his core convictions are and how he would differ from George Bush on the three or four big issues facing the country," said Will Marshall, the president of the liberal-leaning Progressive Policy Institute, who appeared on VOA's Focus program.

Both candidates have curtailed their campaign activities this week to prepare for Thursday's initial debate.

Conservative activist David Keene says the stakes could not be higher for Senator Kerry in the upcoming debates. Mr. Keene is chairman of the American Conservative Union and also appeared on Focus.

"The debates are John Kerry's last chance. If both sides have an equally effective get out the vote operation [within the Democratic and Republican parties], then it is going to turn on those few people who are in the middle and there are fewer people in the middle this year than at any time in modern American history," said Mr. Keene.

For months now, public opinion polls have suggested that the country is sharply divided into two camps, one that supports President Bush and the other that opposes him. The polls also indicate there are fewer undecided voters in this year's election than in recent times.

University of Virginia political expert Larry Sabato says no matter how small a group they may be, undecided voters will still be the primary target for both candidates during the three presidential debates.

"They sit there and do a kind of calculation," said Mr. Sabato. "How many issues that are important to them do they agree with Bush on? How many do they agree with Kerry on? And once the debates are over they finally make up their minds."

The Bush and Kerry campaigns have agreed to 32 pages of rules governing the debates that prohibit the candidates from directly addressing each other. Both men will answer questions posed by a moderator.

Historically, televised debates have often had an impact on presidential elections, especially in close elections such as those in 1960, 1976 and 2000.